Contact means for thermostatic control switch



M. HANTACK Nov. 12, 1957 CONTACT MEANS FOR THERMOSTATIC CONTROL SWITCH Filed March '7, 1955 FIGJ,

FIGA,

FIGB.

nited States Patent Otice 2,813,180 Patented Nov. 12, 1957 CONTACT MEANS FOR THERMOSTATIC CONTROL SWITCH Melvin Hantack, Ferguson, Mo., assignor to McQuay- Norris Manufacturing Company, St. Louis, Mo., a corporation of Delaware Application March 7, 1955, Serial No. 492,463

1 Claim. (Cl. 200-166) This invention relates to contact means for switches, and more particular to enclosed contacts.

A pilot-igniter control generally has an electric igniter coil for igniting the gas and a thermostatic switch for deenergizing the coil after the gas is ignited. Various thermostatic switches have been used for this purpose. For example, a liquid-lilled bulb may be mounted beside the gas jet and connected through tubing to a sealed Switch unit. In such a control, all operative parts are enclosed, but the device is bulky and costly. Another type of thermostatic device employs a heat-sensitive metallic element, such as an expansible rod, which is connected through a mechanical linkage to one of two cooperating contacts. Although this is a simple low cost device, it is diicult to protect the contacts from dust and other foreign matter, which interfere with closure of the contacts. It will be understood that the size and cost of such thermostatic switches are items of major importance, especially in applications such as pilot-igniter controls, hence conventional housings are not entirely satisfactory.

Accordingly, it is an object of the present invention to provide an improved thermostatically controlled switch, wherein the contacts are completely enclosed without enclosing the other elements of the control. Among the several other objects of the invention may be noted the provision of a control of the class described which is extremely simple to construct and of very low cost; and the provision of a low-cost pilot-igniter control wherein the contacts of the thermostatic switch are protected from foreign matter carried in an air stream over the gas jet, as in a clothes drier.

Briefly, the control herein disclosed in detail comprises an expansible heat-sensitive element and a pair of opposed contacts, one of which is coupled for actuation by the heat-sensitive element. The contacts are mounted on a pair of opposed arms for relative movement. Preferably, the contact arms are resilient metallic strips of substantial width and the contacts project from the arms as bosses of less width. A resilient sleeve is then interposed between the contact arms with its ends abutting against the contact-supporting arms in sealing relationship about the contacts. Preferably, the sleeve is formed of silicone rubber, and the contacts are the only elements enclosed. In an igniter, the heat-sensitive element would be mounted beside a gas jet, and the contacts would be connected to deenergize the igniter coil.

Other features of the invention will be in part apparent from and in part pointed out in the following detail description taken in connection with the accompanying drawings, in which:

Fig. l is a side elevation of a control embodying teatures of this invention;

Fig. 2 is a top plan view of the control;

Fig. 3 is a sectional view taken on the line 3 3 of Fig. 1.

Fig. 4 is a detail sectional view illustrating the contacts and their enclosure; and

Fig. 5 is a view similar to that of Fig. 4, but illustrating an alternative embodiment of the invention.

Referring now to the drawings, there is shown an igniter control comprising a body 1 which has a longitudinal passage adapted to be connected at its lower end 3 to a gas supply line. The upper end 5 of the body forms a gas jet for the pilot, an electric igniter coil 7 being mounted on one side of the jet 5 and an expansible heat-sensitive element 9 being mounted on the opposite side. Passages 11 may be formed in the sides of the jet 5 to direct a portion of the gas to the igniter coil 7 and the heat-sensitive element 9 and wind guards 10 may project on opposite sides of the jet. The igniter may be a small platinum coil which is supported upon ceramic blocks 13 with terminal members 15 provided for the connection of electric wires. It will be understood that an automatic valve is opened to supply gas to the jet at the start of a heating cycle. Simultaneously, the igniter is energized, and, after a short period of time, is heated to the point of igniting the gas. The igniter circuit, in turn, is under control of a thermostatically controlled switch, which is responsive to the presence or absence of a flame at the gas jet. Once the gas is ignited, the heat-sensitive element is thereby heated. As the heatsensitive element expands, the contacts are actuated and the igniter is deenergized, thereby prolonging its life.

In the illustrated embodiment, the heat-sensitive element 9 is a rod of stainless steel, one end of which is ixed at 17 and the other end of which is connected to the end of a lever 19. The lever extends through a slot 21 in a bracket 23 and is pivotally supported on one edge of the slot. Its other end is arranged to actuate contacts 25 and 27.

The contacts are supported upon the upper ends of a pair of opposed arms 29 and 31, in the form of resilient metallic strips. These strips, in turn, are sandwiched at their lower ends within a holding assembly 33 xed to the bracket 23. The lever carries a set screw 35, which bears against the contact arm 29, the set screw being adjusted so that the contacts are open when the rod 9 is cold. When the rod is heated by impingement of a flame, the resulting expansion is sucient to close the contacts by movement of the screw 35.

It will be understood that the contacts 25 and 27 are adapted to control energization of the igniter coil 7. In this instance, the contacts are normally open and would operate a relay, which disconnects the coil when the contacts 25 and 27 close. The pilot igniter control is used in conjunction with a main burner. When the appliance requires heat, a valve is opened to supply gas to the pilot jet and the igniter coil 7 is energized simultaneously. Gas issuing from the jet is ignited by the igniter coil, whereupon the expansible rod 9 is heated an amount suicient to actuate the contacts 25 and 27. When these contacts are closed, the igniter coil is deenergized, and gas may be supplied to the main burner. If desired, the entire control may also include a timing device for deenergizing the igniter and shutting down the pilot, if the gas issuing from the jet is not ignited within a predetermined time, although such matters are incidental to this invention.

Usually, the igniter control is mounted directly in the air stream for the main burner, with the result that foreign matter drawn in by the air stream may collect upon the contacts 25 and 27. In such event, the contacts would not operate properly and a closed-circuit condition may not be established. Accordingly, the invention additionally contemplates the provision of a resilient sleeve 37 enclosing the contacts and interposed between and engaging the contact-supporting strips 29 and 31. The contacts are formed as relatively narrow projecting beneath the large contact 21.Y The opposite end of the i sleeve `is feathered to facilitate relative movement 1beyond the contacts. `V

From ltheV foregoing jdescription, it is apparent that those skilled in the art will understand the structure, function and mode of operation-of the invention herein disclosed, and appreciate the advantages thereof. Although one embodiment has beenrdisclosed in detail, it is to be understood that the invention is not lim-ited thereto, but the drawings and description thereof are to be understood as being merely illustrative. For example, the contacts might vbe normally closed, with the lever 19 being arranged to open the contacts upon eX- pansion ofthe rod 9. Alternatively, as shown in'Fig. 5, the sleeve may have a snugtelescoped fit with the larger contacts. VIt is realized that many rnodications and variations will present themselves to those skilled in the art without departing from the spirit of this invention or the scope thereof as set forth in the appended claim.

Having thus described the invention, what isrclaimed and desired to be secured by Letters Patent is:

In a switch having a pair of cooperating contacts and means for moving said contacts into and out of engagement with one another; the improvement wherein said contacts are mounted upon associated resilient strips of a width substantially greater than the diameter of the associated contact, a resilient sleeve interposed between said strips with its ends in sealing engagement with the respective opposed faces of the strips and otherwise encircling the contacts, at least one of said contacts being of an outer diameter substantially less than the inner diameter of the adjacent end of said sleeve, and said sleeve being tapered to a feathered edge in engagement with one of said resilient strips, the resistance to axial compression of said sleeve being substantially less than the resilience of said strips, whereby Vmovement of one strip Atoward the other results in collapse of the sleeve prior to deflection of said other resilient strip.

References ICited'in-the le of this patent UNlTED STATES PATENTS 449,302 Varley Mar. 31, 1891 473,717 Varley Apr. 26, 1892 2,202,207 Johnson May 28, 1940 2,343,060 Horningy Feb. 29, 1944 2,367,441 Schwinn Jan. 16, l1945 2,694,117 Bakke Nov. 9, 1954 

